Circle of Fourths?
Once in a while, the Circle of Fifths might be referred to as the “Circle of Fourths”. This is because if you move around the circle counterclockwise, you will see the progression moves by fourths (spans four adjacent notes).
What is the Circle of Fifths used for?
◉ A bit like a musical version of the periodic table, the letters can either represent notes, chords, or keys.
◉ The circle groups together all 12 major keys with their relative minors (a relative key is defined as the minor key that uses the same notes as a particular major key, or a major key that uses the same notes as a particular minor key).
◉ It tells us how many sharps or flats are in each key: as you go clockwise from the top, each key adds one more sharp until you get to seven sharps (C# major); going counterclockwise from the top tells us the number of flats, adding a flat to every key until you end up with seven flats (Cb major).
◉ Without going into extensive detail, it also tells us what chords are available in each key, can help transpose music into a different key, and can help to move between keys in a song.